How come some fruits and veggies are red, and some are blue? Anthocyanins!
We have had volunteer named Maritza Sirven with us in the Allen kitchen for a little over a year. Maritza is a food science student and researcher at Texas A&M University. She is currently supporting research in her department on the extraction of anthocyanins from potatoes as a potential natural food dye source. Maritza and I wrote the following post to share a little bit about these amazing little helpers in your food.
Anthocyanins are organic compounds responsible for giving reddish and bluish color to various fruits, veggies, and even flowers. Besides blueberries, like the ones we served in our pancakes at Fun Friday breakfast, and the blackberries in the cobbler we served on Tuesday, many delicious fruits and vegetables have anthocyanins in them. These compounds are also present in deep red roses, strawberries, some carrots, red cabbage, and red grapes. That means that the cran-grape juices we serve have them, as well. However, the rich colors that anthocyanins create in fresh fruits and vegetables not only make them beautiful, but good for you, too!
This is because anthocyanins are a type of polyphenolic organic compounds that serve as a secondary metabolites in plants. Big words, right? Let me explain for you. A metabolite is a substance necessary for the metabolism in a plant, which basically means for the healthy operation of a plant. Primary metabolites are compounds that are absolutely necessary for a plant to live. Secondary metabolites are still important to a plant, but are intended to help a plant by carrying out special functions that support the primary ones. For example, polyphenols like anthocyanins are involved in a plant’s defense against ultraviolet radiation, very much like sunscreen for the plant, and they also help defend a plant against certain diseases. This helps plants grow strong and healthy fruit, which means healthy food for us.
In food, polyphenols affect how we perceive foods. They can add color, flavor, smell, and they can also help with something called oxidative stability. Oxidation is a term that refers to the way oxygen molecules interact with other substances. In living things like people and plants, oxidation can damage cells by robbing them of compounds they need, that bond to oxygen molecules. This makes these cells go looking for replacements for the missing compounds, which can start a chain reaction of cells damaging other cells. We call these damaged cells “free radicals”. As such, oxidative stability helps a plant prevent damage from oxidation by slowing down these chain reactions. This is why anthocyanins are sometimes called “antioxidants”. This means that the compounds responsible for the beautiful reds, and blue, and purples in fruits and veggies are actually very good for you!
Now, the difference whether a fruit with anthocyanins becomes red, or blue, or purple, has to do with its pH level, or its level of acidity. Th more acidic the environment inside that fruit, the more red it becomes, while a less acidic environment inside can make a fruit purple or blue. Chefs understand all about acidity. Many of our ingredients are actually acids or bases. Vinegars for example, are acidic. If I add an acid like apple cider vinegar to a fruit that has anthocyanins in it, the color of that fruit may become brighter or more red. But if I add a base like baking soda to water, and then place my fruit in this mixture, the fruit will become more blue in color. Bases are the opposite of acidic, which is also called alkaline. It is just amazing how these tiny little compounds have such big impact on food!
While these colors are amazing naturally in the fruits and veggies we eat, scientists are trying to learn how to extract those anthocyanins from fruits and veggies and use them as pigments for other foods. This is because many foods use artificial colors developed from inorganic sources to give them color. If you ever look at the ingredients of a package of food and you read something with a number like, “Allura Red (Red Dye #40)”, that is an artificial food coloring agent. Many candies, cereals, and other foods use these artificial colors. Scientists are looking for ways to use anthocyanin from fruits as an alternative source to make natural food pigments. So imagine that! Anthocyanins may one day not only serve as a natural way to give food colors, but additionally serve as a source of antioxidants!
Chef Dave and Maritza